linux-kernel - Re: [PATCH 1/3] soc: samsung: exynos-pmu: allow specifying read & write access tables for secure regmap

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Message-ID: <CAPLW+4=mVbXex9Sxm2oEq0j3RJ0_KtXRq2Ttt5cfQ_dxXTuhSA@mail.gmail.com>
Date: Fri, 3 Oct 2025 12:22:46 -0500
From: Sam Protsenko <semen.protsenko@...aro.org>
To: André Draszik <andre.draszik@...aro.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>, 
	Peter Griffin <peter.griffin@...aro.org>, Tudor Ambarus <tudor.ambarus@...aro.org>, 
	Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] soc: samsung: exynos-pmu: allow specifying read &
 write access tables for secure regmap

On Thu, Oct 2, 2025 at 5:33 AM André Draszik <andre.draszik@...aro.org> wrote:
>
> Accessing non-existent PMU registers causes an SError, halting the
> system.
>
> regmap can help us with that by allowing to pass the list of valid
> registers as part of the config during creation. When this driver
> creates a new regmap itself rather than relying on
> syscon_node_to_regmap(), it's therefore easily possible to hook in
> custom access tables for valid read and write registers.
>
> Specifying access tables avoids SErrors for invalid registers and
> instead the regmap core can just return an error. Outside drivers, this
> is also helpful when using debugfs to access the regmap.
>
> Make it possible for drivers to specify read and write tables to be
> used on creation of the secure regmap.
>
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
> ---
>  drivers/soc/samsung/exynos-pmu.c | 3 +++
>  drivers/soc/samsung/exynos-pmu.h | 4 ++++
>  2 files changed, 7 insertions(+)
>
> diff --git a/drivers/soc/samsung/exynos-pmu.c b/drivers/soc/samsung/exynos-pmu.c
> index 22c50ca2aa79bf1945255ee6cc7443d7309b2573..9f416de03610b1727d8cc77616e5c87e2525cc69 100644
> --- a/drivers/soc/samsung/exynos-pmu.c
> +++ b/drivers/soc/samsung/exynos-pmu.c
> @@ -635,6 +635,9 @@ static int exynos_pmu_probe(struct platform_device *pdev)
>                 pmu_regmcfg = regmap_smccfg;
>                 pmu_regmcfg.max_register = resource_size(res) -
>                                            pmu_regmcfg.reg_stride;
> +               pmu_regmcfg.wr_table = pmu_context->pmu_data->wr_table;
> +               pmu_regmcfg.rd_table = pmu_context->pmu_data->rd_table;
> +

Seems like pmu_regmcfg declaration can be pulled under this "if" scope
-- just a thought for future.

>                 /* Need physical address for SMC call */
>                 regmap = devm_regmap_init(dev, NULL,
>                                           (void *)(uintptr_t)res->start,
> diff --git a/drivers/soc/samsung/exynos-pmu.h b/drivers/soc/samsung/exynos-pmu.h
> index 0938bb4fe15f439e2d8bddeec51b6077e79a7e84..113149ed32c88a09b075be82050c26970e4c0620 100644
> --- a/drivers/soc/samsung/exynos-pmu.h
> +++ b/drivers/soc/samsung/exynos-pmu.h
> @@ -27,6 +27,10 @@ struct exynos_pmu_data {
>         void (*pmu_init)(void);
>         void (*powerdown_conf)(enum sys_powerdown);
>         void (*powerdown_conf_extra)(enum sys_powerdown);
> +
> +       /* for the pmu_secure case */
> +       const struct regmap_access_table *rd_table;
> +       const struct regmap_access_table *wr_table;

Maybe it's worth to add #include <linux/regmap.h> in this header, or
at least forward declaration struct regmap_access_table?

Also, would be nice to have kernel-doc comment for struct
exynos_pmu_data at this point, but it might be out of scope for this
patch.

Other than those minor nitpicks -- LGTM:

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>

>  };
>
>  extern void __iomem *pmu_base_addr;
>
> --
> 2.51.0.618.g983fd99d29-goog
>
>